/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.tomcat.util.net;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import javax.net.ssl.SSLEngine;
import javax.net.ssl.SSLEngineResult;
import javax.net.ssl.SSLEngineResult.HandshakeStatus;
import javax.net.ssl.SSLEngineResult.Status;
import java.nio.channels.Selector;
import org.apache.tomcat.util.MutableInteger;

/**
 * 
 * Implementation of a secure socket channel
 * 
 * @author Filip Hanik
 * @version 1.0
 */

public class SecureNioChannel extends NioChannel {

	protected ByteBuffer netInBuffer;
	protected ByteBuffer netOutBuffer;

	protected SSLEngine sslEngine;

	protected boolean initHandshakeComplete = false;
	protected HandshakeStatus initHandshakeStatus; // gets set by begin
													// handshake

	protected boolean closed = false;
	protected boolean closing = false;

	protected NioSelectorPool pool;

	public SecureNioChannel(SocketChannel channel, SSLEngine engine,
			ApplicationBufferHandler bufHandler, NioSelectorPool pool)
			throws IOException {
		super(channel, bufHandler);
		this.sslEngine = engine;
		int appBufSize = sslEngine.getSession().getApplicationBufferSize();
		int netBufSize = sslEngine.getSession().getPacketBufferSize();
		// allocate network buffers - TODO, add in optional direct non-direct
		// buffers
		if (netInBuffer == null)
			netInBuffer = ByteBuffer.allocateDirect(netBufSize);
		if (netOutBuffer == null)
			netOutBuffer = ByteBuffer.allocateDirect(netBufSize);

		// selector pool for blocking operations
		this.pool = pool;

		// ensure that the application has a large enough read/write buffers
		// by doing this, we should not encounter any buffer overflow errors
		bufHandler.expand(bufHandler.getReadBuffer(), appBufSize);
		bufHandler.expand(bufHandler.getWriteBuffer(), appBufSize);
		reset();
	}

	public void reset(SSLEngine engine) throws IOException {
		this.sslEngine = engine;
		reset();
	}

	public void reset() throws IOException {
		super.reset();
		netOutBuffer.position(0);
		netOutBuffer.limit(0);
		netInBuffer.position(0);
		netInBuffer.limit(0);
		initHandshakeComplete = false;
		closed = false;
		closing = false;
		// initiate handshake
		sslEngine.beginHandshake();
		initHandshakeStatus = sslEngine.getHandshakeStatus();
	}

	public int getBufferSize() {
		int size = super.getBufferSize();
		size += netInBuffer != null ? netInBuffer.capacity() : 0;
		size += netOutBuffer != null ? netOutBuffer.capacity() : 0;
		return size;
	}

	// ===========================================================================================
	// NIO SSL METHODS
	// ===========================================================================================
	/**
	 * returns true if the network buffer has been flushed out and is empty
	 * 
	 * @return boolean
	 */
	public boolean flush(boolean block, Selector s, long timeout,
			MutableInteger lastWrite) throws IOException {
		if (!block) {
			flush(netOutBuffer);
		} else {
			pool.write(netOutBuffer, this, s, timeout, block, lastWrite);
		}
		return !netOutBuffer.hasRemaining();
	}

	/**
	 * Flushes the buffer to the network, non blocking
	 * 
	 * @param buf
	 *            ByteBuffer
	 * @return boolean true if the buffer has been emptied out, false otherwise
	 * @throws IOException
	 */
	protected boolean flush(ByteBuffer buf) throws IOException {
		int remaining = buf.remaining();
		if (remaining > 0) {
			int written = sc.write(buf);
			return written >= remaining;
		} else {
			return true;
		}
	}

	/**
	 * Performs SSL handshake, non blocking, but performs NEED_TASK on the same
	 * thread.<br>
	 * Hence, you should never call this method using your Acceptor thread, as
	 * you would slow down your system significantly.<br>
	 * The return for this operation is 0 if the handshake is complete and a
	 * positive value if it is not complete. In the event of a positive value
	 * coming back, reregister the selection key for the return values
	 * interestOps.
	 * 
	 * @param read
	 *            boolean - true if the underlying channel is readable
	 * @param write
	 *            boolean - true if the underlying channel is writable
	 * @return int - 0 if hand shake is complete, otherwise it returns a
	 *         SelectionKey interestOps value
	 * @throws IOException
	 */
	public int handshake(boolean read, boolean write) throws IOException {
		if (initHandshakeComplete)
			return 0; // we have done our initial handshake

		if (!flush(netOutBuffer))
			return SelectionKey.OP_WRITE; // we still have data to write

		SSLEngineResult handshake = null;

		while (!initHandshakeComplete) {
			switch (initHandshakeStatus) {
			case NOT_HANDSHAKING: {
				// should never happen
				throw new IOException("NOT_HANDSHAKING during handshake");
			}
			case FINISHED: {
				// we are complete if we have delivered the last package
				initHandshakeComplete = !netOutBuffer.hasRemaining();
				// return 0 if we are complete, otherwise we still have data to
				// write
				return initHandshakeComplete ? 0 : SelectionKey.OP_WRITE;
			}
			case NEED_WRAP: {
				// perform the wrap function
				handshake = handshakeWrap(write);
				if (handshake.getStatus() == Status.OK) {
					if (initHandshakeStatus == HandshakeStatus.NEED_TASK)
						initHandshakeStatus = tasks();
				} else {
					// wrap should always work with our buffers
					throw new IOException("Unexpected status:"
							+ handshake.getStatus() + " during handshake WRAP.");
				}
				if (initHandshakeStatus != HandshakeStatus.NEED_UNWRAP
						|| (!flush(netOutBuffer))) {
					// should actually return OP_READ if we have NEED_UNWRAP
					return SelectionKey.OP_WRITE;
				}
				// fall down to NEED_UNWRAP on the same call, will result in a
				// BUFFER_UNDERFLOW if it needs data
			}
			case NEED_UNWRAP: {
				// perform the unwrap function
				handshake = handshakeUnwrap(read);
				if (handshake.getStatus() == Status.OK) {
					if (initHandshakeStatus == HandshakeStatus.NEED_TASK)
						initHandshakeStatus = tasks();
				} else if (handshake.getStatus() == Status.BUFFER_UNDERFLOW) {
					// read more data, reregister for OP_READ
					return SelectionKey.OP_READ;
				} else {
					throw new IOException("Invalid handshake status:"
							+ initHandshakeStatus + " during handshake UNWRAP.");
				}// switch
				break;
			}
			case NEED_TASK: {
				initHandshakeStatus = tasks();
				break;
			}
			default:
				throw new IllegalStateException("Invalid handshake status:"
						+ initHandshakeStatus);
			}// switch
		}// while
		// return 0 if we are complete, otherwise reregister for any activity
		// that
		// would cause this method to be called again.
		return initHandshakeComplete ? 0
				: (SelectionKey.OP_WRITE | SelectionKey.OP_READ);
	}

	/**
	 * Executes all the tasks needed on the same thread.
	 * 
	 * @return HandshakeStatus
	 */
	protected SSLEngineResult.HandshakeStatus tasks() {
		Runnable r = null;
		while ((r = sslEngine.getDelegatedTask()) != null) {
			r.run();
		}
		return sslEngine.getHandshakeStatus();
	}

	/**
	 * Performs the WRAP function
	 * 
	 * @param doWrite
	 *            boolean
	 * @return SSLEngineResult
	 * @throws IOException
	 */
	protected SSLEngineResult handshakeWrap(boolean doWrite) throws IOException {
		// this should never be called with a network buffer that contains data
		// so we can clear it here.
		netOutBuffer.clear();
		// perform the wrap
		SSLEngineResult result = sslEngine.wrap(bufHandler.getWriteBuffer(),
				netOutBuffer);
		// prepare the results to be written
		netOutBuffer.flip();
		// set the status
		initHandshakeStatus = result.getHandshakeStatus();
		// optimization, if we do have a writable channel, write it now
		if (doWrite)
			flush(netOutBuffer);
		return result;
	}

	/**
	 * Perform handshake unwrap
	 * 
	 * @param doread
	 *            boolean
	 * @return SSLEngineResult
	 * @throws IOException
	 */
	protected SSLEngineResult handshakeUnwrap(boolean doread)
			throws IOException {

		if (netInBuffer.position() == netInBuffer.limit()) {
			// clear the buffer if we have emptied it out on data
			netInBuffer.clear();
		}
		if (doread) {
			// if we have data to read, read it
			int read = sc.read(netInBuffer);
			if (read == -1)
				throw new IOException("EOF encountered during handshake.");
		}
		SSLEngineResult result;
		boolean cont = false;
		// loop while we can perform pure SSLEngine data
		do {
			// prepare the buffer with the incoming data
			netInBuffer.flip();
			// call unwrap
			result = sslEngine.unwrap(netInBuffer, bufHandler.getReadBuffer());
			// compact the buffer, this is an optional method, wonder what would
			// happen if we didn't
			netInBuffer.compact();
			// read in the status
			initHandshakeStatus = result.getHandshakeStatus();
			if (result.getStatus() == SSLEngineResult.Status.OK
					&& result.getHandshakeStatus() == HandshakeStatus.NEED_TASK) {
				// execute tasks if we need to
				initHandshakeStatus = tasks();
			}
			// perform another unwrap?
			cont = result.getStatus() == SSLEngineResult.Status.OK
					&& initHandshakeStatus == HandshakeStatus.NEED_UNWRAP;
		} while (cont);
		return result;
	}

	/**
	 * Sends a SSL close message, will not physically close the connection here.<br>
	 * To close the connection, you could do something like
	 * 
	 * <pre>
	 * &lt;code&gt;
	 *   close();
	 *   while (isOpen() &amp;&amp; !myTimeoutFunction()) Thread.sleep(25);
	 *   if ( isOpen() ) close(true); //forces a close if you timed out
	 * &lt;/code&gt;
	 * </pre>
	 * 
	 * @throws IOException
	 *             if an I/O error occurs
	 * @throws IOException
	 *             if there is data on the outgoing network buffer and we are
	 *             unable to flush it
	 * @todo Implement this java.io.Closeable method
	 */
	public void close() throws IOException {
		if (closing)
			return;
		closing = true;
		sslEngine.closeOutbound();

		if (!flush(netOutBuffer)) {
			throw new IOException(
					"Remaining data in the network buffer, can't send SSL close message, force a close with close(true) instead");
		}
		// prep the buffer for the close message
		netOutBuffer.clear();
		// perform the close, since we called sslEngine.closeOutbound
		SSLEngineResult handshake = sslEngine.wrap(getEmptyBuf(), netOutBuffer);
		// we should be in a close state
		if (handshake.getStatus() != SSLEngineResult.Status.CLOSED) {
			throw new IOException(
					"Invalid close state, will not send network data.");
		}
		// prepare the buffer for writing
		netOutBuffer.flip();
		// if there is data to be written
		flush(netOutBuffer);

		// is the channel closed?
		closed = (!netOutBuffer.hasRemaining() && (handshake
				.getHandshakeStatus() != HandshakeStatus.NEED_WRAP));
	}

	/**
	 * Force a close, can throw an IOException
	 * 
	 * @param force
	 *            boolean
	 * @throws IOException
	 */
	public void close(boolean force) throws IOException {
		try {
			close();
		} finally {
			if (force || closed) {
				closed = true;
				sc.socket().close();
				sc.close();
			}
		}
	}

	/**
	 * Reads a sequence of bytes from this channel into the given buffer.
	 * 
	 * @param dst
	 *            The buffer into which bytes are to be transferred
	 * @return The number of bytes read, possibly zero, or <tt>-1</tt> if the
	 *         channel has reached end-of-stream
	 * @throws IOException
	 *             If some other I/O error occurs
	 * @throws IllegalArgumentException
	 *             if the destination buffer is different than
	 *             bufHandler.getReadBuffer()
	 * @todo Implement this java.nio.channels.ReadableByteChannel method
	 */
	public int read(ByteBuffer dst) throws IOException {
		// if we want to take advantage of the expand function, make sure we
		// only use the ApplicationBufferHandler's buffers
		if (dst != bufHandler.getReadBuffer())
			throw new IllegalArgumentException(
					"You can only read using the application read buffer provided by the handler.");
		// are we in the middle of closing or closed?
		if (closing || closed)
			return -1;
		// did we finish our handshake?
		if (!initHandshakeComplete)
			throw new IllegalStateException(
					"Handshake incomplete, you must complete handshake before reading data.");

		// read from the network
		int netread = sc.read(netInBuffer);
		// did we reach EOF? if so send EOF up one layer.
		if (netread == -1)
			return -1;

		// the data read
		int read = 0;
		// the SSL engine result
		SSLEngineResult unwrap;
		do {
			// prepare the buffer
			netInBuffer.flip();
			// unwrap the data
			unwrap = sslEngine.unwrap(netInBuffer, dst);
			// compact the buffer
			netInBuffer.compact();

			if (unwrap.getStatus() == Status.OK
					|| unwrap.getStatus() == Status.BUFFER_UNDERFLOW) {
				// we did receive some data, add it to our total
				read += unwrap.bytesProduced();
				// perform any tasks if needed
				if (unwrap.getHandshakeStatus() == HandshakeStatus.NEED_TASK)
					tasks();
				// if we need more network data, then bail out for now.
				if (unwrap.getStatus() == Status.BUFFER_UNDERFLOW)
					break;
			} else if (unwrap.getStatus() == Status.BUFFER_OVERFLOW && read > 0) {
				// buffer overflow can happen, if we have read data, then
				// empty out the dst buffer before we do another read
				break;
			} else {
				// here we should trap BUFFER_OVERFLOW and call expand on the
				// buffer
				// for now, throw an exception, as we initialized the buffers
				// in the constructor
				throw new IOException("Unable to unwrap data, invalid status: "
						+ unwrap.getStatus());
			}
		} while ((netInBuffer.position() != 0)); // continue to unwrapping as
													// long as the input buffer
													// has stuff
		return (read);
	}

	/**
	 * Writes a sequence of bytes to this channel from the given buffer.
	 * 
	 * @param src
	 *            The buffer from which bytes are to be retrieved
	 * @return The number of bytes written, possibly zero
	 * @throws IOException
	 *             If some other I/O error occurs
	 * @todo Implement this java.nio.channels.WritableByteChannel method
	 */
	public int write(ByteBuffer src) throws IOException {
		if (src == this.netOutBuffer) {
			// we can get here through a recursive call
			// by using the NioBlockingSelector
			int written = sc.write(src);
			return written;
		} else {
			// make sure we can handle expand, and that we only use on buffer
			if ((!this.isSendFile()) && (src != bufHandler.getWriteBuffer()))
				throw new IllegalArgumentException(
						"You can only write using the application write buffer provided by the handler.");
			// are we closing or closed?
			if (closing || closed)
				throw new IOException("Channel is in closing state.");

			// the number of bytes written
			int written = 0;

			if (!flush(netOutBuffer)) {
				// we haven't emptied out the buffer yet
				return written;
			}

			/*
			 * The data buffer is empty, we can reuse the entire buffer.
			 */
			netOutBuffer.clear();

			SSLEngineResult result = sslEngine.wrap(src, netOutBuffer);
			written = result.bytesConsumed();
			netOutBuffer.flip();

			if (result.getStatus() == Status.OK) {
				if (result.getHandshakeStatus() == HandshakeStatus.NEED_TASK)
					tasks();
			} else {
				throw new IOException(
						"Unable to wrap data, invalid engine state: "
								+ result.getStatus());
			}

			// force a flush
			flush(netOutBuffer);

			return written;
		}
	}

	@Override
	public int getOutboundRemaining() {
		return netOutBuffer.remaining();
	}

	@Override
	public boolean flushOutbound() throws IOException {
		int remaining = netOutBuffer.remaining();
		flush(netOutBuffer);
		int remaining2 = netOutBuffer.remaining();
		return remaining2 < remaining;
	}

	/**
	 * Callback interface to be able to expand buffers when buffer overflow
	 * exceptions happen
	 */
	public static interface ApplicationBufferHandler {
		public ByteBuffer expand(ByteBuffer buffer, int remaining);

		public ByteBuffer getReadBuffer();

		public ByteBuffer getWriteBuffer();
	}

	public ApplicationBufferHandler getBufHandler() {
		return bufHandler;
	}

	public boolean isInitHandshakeComplete() {
		return initHandshakeComplete;
	}

	public boolean isClosing() {
		return closing;
	}

	public SSLEngine getSslEngine() {
		return sslEngine;
	}

	public ByteBuffer getEmptyBuf() {
		return emptyBuf;
	}

	public void setBufHandler(ApplicationBufferHandler bufHandler) {
		this.bufHandler = bufHandler;
	}

	public SocketChannel getIOChannel() {
		return sc;
	}

}